Ping check
I've suggested this before and usually people seem to like the idea, but for some reason riot has yet to implement this feature.
Once per day, on your first login to the client from any device, before you can start any pvp games you must pass a ping check.
To pass the ping check, certain parameters must be met.
your ping must be < 200ms your ping must be stable, any fluctuation during the test >30% will result in a fail
Personally I would argue that 200ms ping is still too high, but as long as its holding steady whatever.
Anything above 200ms would basically mean you are playing in another region anyway, and therefore should not be on NA servers to begin with. Either that or your connection is really just that terrible, and you shouldn't be allowed to ruin the game for other people due to your bad connection.
As for the ping fluctuation test, this is a bit less common, but there are times where people who have otherwise good connetions start to have issues and may not know it yet, and discover it for the first time in a ranked match. This would alert those people that there is a problem and give them a chance to fix the issue before they continue to play league.